DVI stands for Digital Video Interface, and is a digital standard for connecting monitors, projectors, etc. to their digital video source. There are three types of DVI cables: digital-only, analog-only, and combined (both digital and analog). These are denoted by the terms DVI-D, DVI-A, and DVI-I respectively.

Single Link and Dual Link

DVI cables are further divided into "Single Link" and "Dual Link". Single Link has a maximum display resolution 1920x1080, whereas Dual Link permits 2048x1536. DVI cables manufactured to the Dual Link standard achieve this by having more wires in the cable. These extra wires permit data to be transferred faster, thus higher resolutions are possible. Alternatively, there is the option of driving two separate displays. Please note that these advantages can only be implemented with a video source and display device that both support the Dual Link standard, which at the time of writing is quite rare. A Dual Link cable can be used with Single Link equipment, and tend to be of better manufacturing quality. All DVI cables and adaptors found on the CableCity.co.uk website are Dual Link standard. CableCity.co.uk can supply DVI Single Link cables to the trade, in volume, at a discounted price.

Identifying the DVI variants

In the above diagram, your attention is drawn to a number of features. The Analogue signal is carried on the four pins surrounding the flat metal spade at the end of the connector. Hence, in the DVI-D (Digital) variant, these pins are missing. Whether a cable is Single Link or Dual Link is defined by how the digital signal is connected and carried, hence in the DVI-A (Analogue) variant, there is no distinction between Single Link and Dual Link since no digital signal is carried. Many consider the DVI-A variant to now be obsolete.

Which cable to use, and a special note concerning adaptors

One approach is to simply match up the connectors on your devices. Whilst connectors with differing DVI variants will fit each other, when using adaptors you should take care not to rely on a digital or analogue signal being present unless you have confirmed this. For example, if you have a DVI-D (digital only) output on a video card, you might try to use an adaptor to convert it to a HD15 connector, which are universally used for (S)VGA monitors. Even though this fits together perfectly, this will not work as a (S)VGA signal is analogue and there is no analogue signal present in a DVI-D connector, which is 'digital only'. On the other hand, if the output of the video card is DVI-I (analogue and digital), then it can be expected to work!

Maximum cable lengthDue to the high data rates, DVI cables have an overall maximum length of 5 M. If you need to drive a DVI signal over a longer distance, then you will need to convert the DVI signal so that it can be carried over a fibre-optic cable. Due to cost, this approach is typically limited to professional applications.

What's the difference netween Digital and Analog Interface?

DVI

SVGA

Advantages

Signal losses on cable do not affect picture quality - it works or it doesn't

Clock and phase of the TFTs must be synchronized with the analog signal to avoid pixel jitter, which is a relatively complex issue

Cables sensitive to electrical interference

High cost of signal conversion inside the display

Cannot convert to a digital signal using a simple adaptor

How many Digital Interfaces are there? Currently there are three digital interface standards (P & D (M1DA), DFP, and DVI) in the market. The following table is the comparison and summary of the three interface standards. According to the table, DVI will be a standard in the future. DVI not only allows high resolutions, it also enables the connection of analog devices.

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